1. Field of the Invention
The invention relates to a method of monitoring an area with the aid of a frequency-modulated continuous-wave radar, and to a device for carrying out the method.
2. Background Information
The invention is especially suited for aircraft, e.g., airplanes, as onboard radar so that these can also land safely under unfavorable visibility conditions, i.e. low visibility aircraft landing, e.g., fog. Furthermore, under unfavorable visibility conditions during taxiing, a monitoring of the taxiway located ahead of an aircraft is also possible.
Such an onboard radar requires a small range, e.g., less than 5 km, and a relatively good resolution [sic], e.g., 1 m to 3 m in range direction or 0.1.degree. to 0.5.degree. in azimuth direction. For such applications, the use of a so-called pulse radar is known. This pulse radar has the following disadvantages, inter alia:
the small so-called duty cycle (pulse duty factor), which is due to the required high ratio of range to range resolution, requires the use of a tube transmitter, e.g., a magnetron. This tube transmitter has drawbacks known per se, e.g., a short working life and a high maintenance expenditure (because of the high voltage to be produced); PA1 the required high (transmitting) peak power in connection with a high (transmitting) antenna gain may lead to injuries to health, especially to the eyes. Such a pulse radar is therefore unsuitable, especially for monitoring the taxiways and/or the apron of an airport; PA1 the use of a pulse radar in a so-called high-PRF or pulse compression mode is, in a disadvantageous manner, very cost-intensive and therefore uneconomical; PA1 if several pulse radars are needed in an aircraft, disturbances occur among these in an unfavorable manner. These can only be avoided through cost-ineffective expenditure with regard to the EMC (electromagnetic compatibility).